title: Self-energy effects and electron-phonon coupling in Fe-As superconductors.
abstract: Doping and temperature dependent studies of optical phonon modes in Fe-122 pnictides are performed using Raman scattering experiments and compared with model calculations to elucidate the role of electron-phonon and spin-phonon interaction in this family of compounds. The frequency and linewidth of the B(1g) mode at around 210 cm(-1) is highlighted as appreciable anomalies at the superconducting and spin density wave transitions are observed that strongly depend on composition. We give estimates of the electron-phonon coupling related to this renormalization and calculate the phonon self-energy on the basis of a four-band model comparing different symmetries of the order parameters. In addition, we observe a pronounced quasi-elastic Raman response for the undoped compound, suggesting persisting magnetic fluctuations in the spin density wave state.
authors.affiliation: Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany.
authors.forename: K-Y
authors.initials: KY
authors.lastname: Choi
authors.forename: P
authors.initials: P
authors.lastname: Lemmens
authors.forename: I
authors.initials: I
authors.lastname: Eremin
authors.forename: G
authors.initials: G
authors.lastname: Zwicknagl
authors.forename: H
authors.initials: H
authors.lastname: Berger
authors.forename: G L
authors.initials: GL
authors.lastname: Sun
authors.forename: D L
authors.initials: DL
authors.lastname: Sun
authors.forename: C T
authors.initials: CT
authors.lastname: Lin